Dose response effect of dietary zinc on in vitro digestibility and gas production in sorghum based diet for buffaloes

A study was undertaken to investigate the effect of dietary zinc concentration on in vitro digestibility and gas production. A sorghum stover based diet (29.72 ppm Zn) was formulated to which appropriate amounts of ZnSO₄ was added so as to supply the zinc at 0, 20, 40, 60, 80, 100, 120, 140 and 160 ppm. The in vitro dry matter digestibility (IVDMD) increased in Zn supplemented diets and highest (P<0.01) was observed at 140 ppm Zn concentration. Beyond 140 ppm (160 ppm), no further improvement in IVDMD was observed. The mean gas volume, in vitro organic matter digestibility (IVOMD), metabolizable energy (ME) and short chain fatty acids (SCFA) contents were higher (P<0.01) in Zn supplemented diets and increased up to 140 ppm Zn concentration in a dose dependent manner. At 160 ppm Zn supplementation, the values decreased and were comparable with that of 20 to 60 ppm. The IVDMD, gas production, IVOMD, SCFA and ME content at 140 ppm were though highest, was comparable with that of 80, 100 and 120 ppm Zn addition. Thus the present in vitro study indicated that Zn influenced the nutrient digestibility and dietary Zn supplementation up to 140 ppm improved the digestibility, while depression in digestibility was observed at 160 ppm Zn addition.